The present invention relates to an optical beam monitoring device, and in particular to a device for tapping light from a sealed optical centerpiece for monitoring the light passing therethrough.
Monitoring the various parameters of light traveling in an optical waveguide is typically performed using an optical tap, which directs a small portion of the light to an applicable monitor. Conventional optical taps have taken many forms, including those disclosed in U.S. Pat. No. 4,135,780 issued Jan. 23, 1979 in the name of Richard Dyott; U.S. Pat. No. 4,398,795 issued Aug. 16, 1983 in the name of John Palmer; and U.S. Pat. No. 4,475,789 issued Oct. 9, 1984 in the name of David Kahn. The Palmer Patent relates to measuring the amount of light lost from an optical fiber bent over a solid support, while the Kahn Patent relates to monitoring the light radiated away from a fiber splice. The Dyott Patent discloses one example of, perhaps, the most common optical tapping method, which includes fusing a second optical waveguide beside the original waveguide for collecting light therefrom. Unfortunately, the systems disclosed in the aforementioned patents require several invasive and costly steps to implement.
U.S. Pat. No. 4,995,696 issued Feb. 26, 1991 to Eiichi Nishimura et al; and U.S. Pat. No. 5,523,837 issued Jun. 4, 1996 to Christopher Prozzo disclose optical power meters utilizing beam splitters to tap off a portion of the light for monitoring. Both of these devices require the construction of special housings to accommodate the photodiode, which increases material costs. Moreover, to construct the aforementioned devices, the process would include the added step of sealing the photodiode wiring, which passes through the housing. This adds both to material costs and manufacturing costs.
An object of the present invention is to overcome the shortcomings of the prior art by providing an optical beam monitoring device that does not affect the integrity of the system nor require the manufacture of special housings.
Accordingly, the present invention relates to a light monitoring device comprising:
a first lens for collimating an input light beam;
beam splitter means for separating the input light beam into a tap portion and a through portion, and for directing the tap portion and the through portion in different directions;
second lens for focusing the through portion;
a sleeve enclosing the first lens, the beam splitter means and the second lens, the sleeve including a window, which is at least partially transparent to the tap portion; and
monitoring means disposed externally of the sleeve for receiving the tap portion;
whereby the beam splitter means directs the tap portion through the window to the monitoring means.